Telephone system.



J, [l WBIGHL TELE'PHONESYSTEM. APPLiCATiUN FILED MRR. 7. 19H.

' atsn Emy 6, MM5.

13 SHEETS-SHEET-I.

O QO 3. L. WRlGHT.

ELENIONE SYSTEM, APPucATxoN min MAR. I. 1911.

Patented July 6, 1915.

i3 SHEETS-SHEET 2.

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l 8.10 J k y. n NN mn@ wwm l HHWIVHT o0 NEWNR A NAMQP Lm@ c f l I Il @MM/L 1. L. wRiGHT. TELEPHNE SYSTEM.

APPLICATION -FILED MAR. 7,1911.

Li", Panted July 6, 1915.

13 SHEETS-SHEET 3.

V ZZZ D@ @o 35 N @MMV l l J| ,7,2 O0 V VY r] 9 a g @www oo0 LIZ B 6 E? Fw J. L. WRIGHT. TELEPHONE SYSTEM.

' APPL'ICATION FILED MAR. 7. 19H. 1,145,109.

Patented July 6, 1915.

13 SHEETS-SHEET 4.

. I. WRIGHT.

TELEPHONE SYSTEM.

APPLIS/WON FILED MAR. 1911.

Pa'ente July 5, i915.

13 SHEETS-*SHEET 5.

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S14-wink@ I. L. WRIGHT. TELEPHONE SYSTEM.

APPLICATION FILED MAR. 7, 191|- 1,145,109.

I3 SHEETS-SHEET 6.

Patented July 6, 1915. I

J. L. WRIGHT.

TELEPHONE SYSTEM.

APPUCAUON F1151) 1-1A11.7.1911.

Q., Patented July 6, 1915.

I3 SHEETS-SHEET I.

J. L. WRIGHT.

TELEPHONE SYSTEM.

APPLICATION FILED MAR. 7, 19H. 1,145,109, Patented July 6, 1915.

I3 SHEETS-SHEET 8.

IIIIIH' y J. L. WRIGHT.

TELEPHONE SYSTEM.

APPLICATION FILED MAR. 7, 19H. 1,145,109.

I3 SHEETS--SHEET 9.

Pa'ened July 69 MLS.

1. L. WRIGHT. TELEPHONE SYSTEM.

APPLICATION FILED MAR, 7. 19H. l,l45,109.

I3 SHEETS-SHEET l0.

Patented July 6, 1915.

I. L. WRIGHT. TELEPHONE SYSTEM.

nur@ APPLICATION FILED MAR. 7,1911.

Patented July 6, 1915.

I3 SHEETS-SHEET I l.

I. I.. WRIGHT. TELEPHONESYSTEM.

APPLICATION FILED MAR. Y. I9II I 1,145,109, Patented July 6, 1915.

I3 SHEETS-SHEET I2. o 4 N .0 N I s@ AAA-- y I J. L. WRIGHT.

( TELEPHONE SYSTEM.

APPLICATION FILED MAH. 7, 1911- I 1,145,109. Patented July 6, i915.

Snom/Lt :on party lines Vwithout plete system, and diagrams-as :follows: Fig. 2

lLlNlED JOSEPH L. VJBIGHT, @E CLEVELANQ, FREDERGK C. STEVENS, @3?

FSEOL., 'BY MESNE ASSGMENTS, TO

NEW

TELEFEONE EYSTESJ.

To all whom it may concern Be it kncivn that l, Josnrn L. .Yaicri'r, citizenof the United States. residing at Cleveland, in the county;v of Cuyahoga and State of Ohio, have invented certain new and useful lmprovements in Telephone Systems, of which the following is a specification, reference being had therein to the accompanying drawing.

My invention relates to 'telephone ezichangc systems and especially te senii-auto matic systems in Which incoming calls are distributed among idle operators, `.vho then control selective switches to effect the connections desired.

The general object of this invention is the improvement 03": systems of the class mentioned in divers particulars which will hereinafter appear.

Specific objects may be stated as ollcvfs: to prevent a calling line from remaining connected to a detective trunk; te permit several calls from different groups ol lines to reach a corresponrling` number ci operators key sets simultaneouslv; to permit trunk connections to ce effected by a single act on the part of an operator in less ne than ordinary numerical selections; to p oduce trunk connections between autcinatic and manual sivi'tchinf.,` centers vvith double supervision by the manual operator; te permit the calling subscriber to tree his line and restore the central otlice apparatus at e1157 time after the calling impulses are started from the operators key set, out not heifcreg to 'produce simultaneous drive ef primary and secondaryY switches in a singl of time; tc'prevent the called sul from accidenlmlljvvv releasing the, ccnnec" but to 1permit instant-ananas release ef connector when the called line t to enable an cperator to malte reverting cans up unusa.

trunks or switches. l

My invcnticn is illustrated in the accompanying drawings, in ivlich:

' 'Figure 1 is a skeletondiagram of the coinn Figs. 2 to 12a are detailed scrbers line and the primary control cir cuits` Fig. 2 is a modification; ci the a 'switch control. 3- shos niniary Specification ci Letters latent.

shows a latented July 6, 19%.

serial in. cimas.

and first selector svvitch circuits. Fig. 3 shows second selector eivitch circuit. Fig. 3b is a detail of the release circuit. Fig. 4e a connector switch circuit. Fig. 5

snows the cperatorls trunk circuit with lrej set control. Fig. 6 shows the operator sv key-set an. sending machine circuit. l. 7 is suhscrihers partyline. Fie: S is a detail showing secondary control. Figs. 9 and 1G complementary ligures showing a special sel iter suit-ch permanently connected me operators trunk circuit for making reverting calls. Figs. ll, l2 and 12a shew the trunk center ln this description l will .irst outline the h ystem as shown in l* l5 then briefly refer o the various `pil-ces of apparatus and inalljv take up the circuitsto l2 inclusive, and explain tl in detail.

operaticn each element marke f, for purcses ci? ccmpariscn and tc understanding" y "which in gene" it reughcut 1. ence letters ls shenvn el the rela- 1.-. .vb le may be taten that rer convenienceall calls A .y end cf the sheety Wiles tenninasel en mi ticle contacts of th -a naar? .ivoted einer centact which can he f line contacts tc connect with iret selector trunk; v'fhiclifis a similar lector switch. The. lixed .en these `Wipers sweep in are centact circuits between automatic ancleinployed,

teward the right, the Wanted or called' Each ci' 'these Wipers switches, each of Which-has .95

'lOO

neually re'errecl to as' 5 scrihers lines The bank contacts of the irst selector .switches form the terminals of second selector trunks, each of which is connected to corresponding contacts, that is to say multipled, in all the first selectors. At the right hand ends the second selector trunks terminate at wipers of second selector switches, and from the bank contacts oi I these switches the connector trunks are taken, in multiple as before, to the wipers of connector switches. The banks of these connector switches contain only line terminals, just the same as the primary selectors. At the right hand end ot' Fig. 1 three subare shown, each with four subscribers stations connected to it in parallel. These are party lines, so shown for the purpose of illustrating the principle .of selective. ringing, which forms a part oi" the system. They need not all be party lines however, nor is it necessary that the subscriliers shown on the right of Fig. 1 should he different from those shown at the left.

n the contrary, every subscribefs line, in

order to have complete service, must be connected to terminals in both the primary selector switches and the connector switches, since it is through the former that the subscriber` when calling reaches the central -'otiice, andV it is through the connector switches that the central odice when calling reaches the subscriber. The connections of a line to primary and connector switches .are made in parallel, just as are those ot each line to the several switches of either class.

Associated with each connector switch is an auxiliary or ringing selector switch. The wiper ot this switch sweeps over contacts connected to several ringing generators, each of which feneratesl a particular distinctive character of current. .\t the several stations on a party line the bells are designed and adjusted so as to respond selectively and exclusively, each to its own particular kind ot' current only. At the last stage in a connection, when the wanted subscribers line has been picked out by the connectorv switch,

has been set so as to bring into service. the proper generator, the wiper of tliat switch is then automatically connected through thc connector to the subscribei"s line to ring the bell. At all other times the ringing selector remains disconnected.

The primary. selector switches are controlled by the subscribers in calling, through the medium of line relays at the central oiice which respond to the l'low of current 50 in the subscribers lines, and which when .so energized guidev and direct the primary switch wipers to their respective line contacts.

access to the lirst selector trunks in the cenand the ringing selector' A calling subscriber therefore gains tral oiiiee by hisl own act alone. In order to continue the connection however, from the first selector trunk to the wanted subscriber, it is necessary to actuate a first selector switch. a second selectorswitch and a connector switch. The type ot' switch employed in this system is electromagnctieally driven by means ot' current impulses ot' predetermined number sent in predetermined groups, which move the switch wipers step by step over the bank contacts. rThese impulses ai'e supplied, controlled, by operators at the central otfice, who for that purpose are given access through secondary selector switchesto the tirstselector trunks. whereby they are enabled both to receive their orders from the calling subscribers, by way o't the primary selectors. and to send impulses to the first selector and succeeding switches, for the pui-'pose of making the desired connection. The secondary selector switches as will presently be seen, arc initially responsive to the subscribers acts in calling. In tact, broadly speaking. their operation is the same as that of the primary selector, the flow of current in a calling subseribersl line and in the iii-st selector trunk connected thereto causing a secondary selector switch wiper to be guided and directed automatically to a contact in its bank which is con nected to the first selector trunk in question.

ln order to select and transmit the proper impulses for line selection l provide each operator with a key-set mounted on a suitable desk, and lia\iiig associated with it certain signals which guide the operator in the performance of her duties. The key-set in gcneral appearance and arrangement is quite similar to the key board oi an adding machine or typewriter, consisting ot' a number of strips of ten keys each. numbered from one. to naught in each vertical row. One ot the. signals associated with these keys is a calling lamp, which is lighted auton'iatically when the key set becomes connectedthrough the secondary switch to a first selector truuk already connected to a subscribers line through a primary selector switch. Obs irving the signal, the operator asks 4thesubstiriber Jfor the number wanted, and proceeds to depress the corresponding keys or buttons. 4She then presses a separate starting key, and groups ot' impulses, corresponding to the buttons depressed, will thereuponbe transmitted through the key-set, through the secondary selector switch and through the first selector trunk to the first selector switch, causing the following operations: {l} Thefirst selector switch is stepped around to the contact of a second selector trunk'leading to a. second selector switch in Vthe. thousands group corresponding to the' -first digit set up (2) the secondl selector and the switches arc .set in response to nieuwe switch is stepped around to select a connector trunk leading to a connector switch of the hundreds group corresponding tothe second digit set up, (this particular connector containing terminals of the line wanted) f, (3 and i) the connector switch is then stepped around in response tothe third and fourth groups of impulses to pick out the terminals of the line wanted; and the associated ringing selector having been the operation of the impulses, the wanted subscribers bell is automatically rung.

Reference has been made above to thousands groups 7 and l hundreds groups of ,1. circuits. This particular,switching system is known as a percentage trunlting system. That is to say, the connection between any two lines is eiected by successive steps orV successive acts of subdivision. For example, in an exchange serving ten thousand subscribers, the second selector switches would be divided into ten groups, through one of which access could be had to the connectors containing lines numbered from 1000 to 1999,'through the next, to lines numbered Similarly,

the connectorswitches in each thousands group wouldbe divided into ten su -groups according to their hundreds digit. Through the first rif-these sub-groups, lines numbered ffrom' `00 to 199 could be reached, through fthe second lines numbered from 200 to 299,

.- and so on.

ycould be had 2irst a second selector-'oit' j'in which that by means of that in connectionwith them,

Las this condition is brough bviously therefore, access to any desired line by selecting the thousands group line number occurs, and then selector picking out a connector of the hundreds group in which the line number occurred. That connector would then actually contain terminals of the wanted lines. 0f' course in practice the wiring between the diderent groups of switches is quite complicated because of the large number of trunk wires employed to furnish the various combinations required between the switches, but the theory is quite simple, and is well enough illustrated in Fig. l.

As soon as one f the subscribers at the left of Fig. l has become connected in the ianner stated with one of the subscribers v,at the right, it is unnecessary and in fact unde"rable for the operator to remain longer and means are provided for automatically cutting ofi' and restoring the secondary selector switch as soon t about. Thereafter all the switches in use between the two subscribers are under their own control, and when they iinaily hang up their receivers fthe several switchesare automatically restored, the connection is parts resume the positions of idleness diagraphically illustrated in' Fig. 1.

. necessary broken, and all- .more than one trunk to the same operator,

or more than one operator to the same trunk. Special provision is made howeyer, tov prevent this. At the left of Fig. l l he*v indicated wlgat l call a primary distributing switch and a secondary distributing switch. T he first of these contains in its banks testing terminals ofthe primary switches or first selector trunks. lt is actuated in response to the subscribers calls, and always acts to select and start up an idle switch and trunk for connection with the calling line. There is only' one distributing switch for all the primary selector switches serving the same group of subscribers, hence only one switch can be started at a time, and this prevents more than one trunk being connected to the same line. ln going to the line, the action of the primary switch is to test overl its bank contacts untilA it reaches a Contact which has had its condition changed, due to current flowing in the calling line. than one line is calling, the switch will stop at the first one to be reached, and thereafter lf more v the distributing switch will start another y primary selector to search for the second calling line, whereby it is impossible 'for more than one line to get on the same trunk.

The secondary distributing switch performs the same functions with respect to the operators or secondary selector switches, and is actuated also in response to the subscribers calls, so as to start only one secondary selector switch at a time for any one group of trunks.

As no claims will be made herein to the mechanical features of the apparatus emfployed, detailed description thereof is unandthe construction and functioning of the several pieces will be sufficiently understood from the detailedstatcment of operation hereinafter, read in connection with the following remarks: The unit of the connectivesystem is a one hundred point switcl of'the same type as that shown in Letters'Patent No. 977,536, grant- "ed December 6,1910, toCharles H. North.

turn therefor, and the v of the present invention,

contacts of the primary switches 8*.

may be found. This is done during the first or rotary motion of the spindle, and when the busy or calling row-contact is found, the switch stops rotating and starts to step up the row designated. The lower or test contacts i025, W and ai, in Figs. 3 and 5 respectively, then slide up the row of individual test contacts until the particular calling contact is reached, when all motion ceases, and as the connective o1" talking contacts fl/.-u-4, furgn-ws1 (Figs. 3 and mOVe'cOnstantly with the test wipers and are alined thereby, the calling line or trunk is thus accurately selected and connected.

The relays throughout the system are preferably of the type shown and described in Letters Patent No. 972,634, granted October 11, 1910, to Charles H. North; but any standard relay may be adapted to this service.

The operators keys employed as shown in Fig. 6 are built in strips, are interlocking, and preferably of the general type shown in Letters vPatent No. 955,134, granted April 19, 1910, to John F. Cadell; but. obviously other standard interlockingr keys may be adapted for this service.

rlhe distributing` switches shown. at S, S', S2, S3, S7 and S'1 in Figs. 2, 5, 4, S and v9, are single motionstep by step electromagnetically driven switches preferably having the driving magnets lnounted as a unit on a short frame'secured to the contact bank. A convenient form for both the bank and stepping magnet with its armature and pawl, is that shown in the aforesaid North patent. Since only the rotary ratchet and the cooperating rotary magnet are employed, no circuit is taken off through the wipers or spindle, each row or set of contacts in the banks being accompanied by a continuous solid-contact constituting a rewipers being in pairs adapted to bridge any unit contact of the set with the common return.

The subscribei"s apparatus forms no part except as it is included for completeness in description, and is of any usual or desired type adapted to common battery circuits. The operators sending machine employed herein is preferably comlnon'to the whole exchange and of the type shown in my prior application, Serial No. 402,033, liled November 13, 1907.

Referring now to Fig. 2, and bearing in mind the general description of Fig. 1, each line circuit l-2 is provided with a. line relay R and a cut-oft' relay R2 which when energized disconnects the line relay R connects the vtip and sleeve sides of the line to its multiple bank contacts in the primary and connector switches of its group. The attraction of the armature r1.2 5 of the relay connects ground to the individual test The relay on shortclrcuit to ground through arma- 2, which prevents interference bv the subscriber 1n case he should The line relays R are divided windings 'of each group are connected in multiple'to the winding of a relay common to the group, which when energized connects ground to the row contact'of the/primary switch through the natin the group of lines calling, while the t designates the particular line in the group.

Each group of one hundred lines is assumed to have access for calling purposes to ten primary selector trunks, such as shown in Fig. 3, and to be accessible for calling through ten connector switches such asI shown in Fig. 4. hns, each line has twenty sets of multiple contacts, mary selector banks, and ten in the conne tor banks. The primary distributing switch determines which trunk in the group of ten being idle, shall respond to any pai'- ticular call in its group of lines; and one of these primary vdistributing switches is therefore required for each group of one -hundred lines, with its ten trunks. ciated with each primary distributing switch there is a secondary distributing switch S2, and a kick-off switch S. The function ot' the secondary' distributing switch is to piek out an idle operators circuit and start the same to testing for the group of primary trunks over which the call originates.

`his can be done because there being only one switch S2 for each group of one hundred lines, that is to say ten trunks such as shown in Fig. 3, and since it is convenient to arrange the contacts of each group of ten trunks in one and the same row in the secondary selector switches SS Fig. 5), each secondary distributing switch can therefore be directly identified with its own associated row of primary trunk contacts in each of the seconda ry selector switches. Furthermore, since each secondary distributing switch S2 has a number of contacts in its bank, these contacts may be individually connected to several secondary switches, the use of multiples for this purpose in the 'switches S2 being thereby avoided, and a great additional advantage gained, in that simultaneous calls may be distributed f `1Terent such as shown in Fig. 2 to diilerent operagures. ge of one thousand lines in which there would beten groups of lines and trunks, with one secfor each group ofv into groups of ten and thev iso 'respectively to `Wires and 757) leading ondary listributing `Witch Ss for each group5 corresponding contacts s2 and s200 niultipled in the ten switches and er the Various secondary switches SS.

The contacts 820 are not multipled out Wired di ect to the row contacts s of the secondary switches SS. Number one switch S2 belonging,w to certain group has its iir contact .20 Wired to number one row conta of the first secondary switch SR. its seconi Contact a2 Wired to number one row con-'Sac of the second secondary switch Si, and so on. Number two switch S2 belong-Ying to another group has its iii-st Contact s Wired to number tivo ronv contact o the rst ondary switch SS. its second Contact se Wired to number two rouv Contact of the second secondary switch S8 and so on. in exchange of one thousand lines the contacts s2 or" the tenth switch S2 are Wired to nurnber ten row contacts of .the secondary svitches S8.

if in an exchange of one thousand lines si-' multaneous calls should come in from each group of one hundred lines and ten secondary selector switches S8 were provided, one row Contact in each switch SS would be made active. lllithout any confusion each switch S8 would test for its active row contact and then find the individual Contact in the row. The individual test contacts would be Inultipled in a group of secondary switches SS so that any switch SS in the group can piel: out any trunk belonging to its group.

The relay R5 has one terminal of its winding connected to the Wiper arm Iws of the switch S. lVhen the arm ws in rotating finds an idle primary switch S the relay R5 is energized in series with the relay l l (Fig. and opens the Circuit or stepping magnet M, thus bringing the switch S to rest., The energizing or" the relay R5 causes the switch S2 to immediat-ely start to pick out an idle secondary switch S8. The switch S* Can be testing for the calling line While the switch S8 is testingl for the trunk shown in Fig. Q. The relay R1 acts some' ihat as the line relay Ri, connecting battery to its individual test contacts in the switches SS.

It will benoticed in the statement of operation hereinafter that the relay R13 is not denergized until the primary switch linds the calling line and the secondary switch SS Finds the trunk connected to line. By this arrangement all confusion is avoided regardless of which srfitcli performs its functions first,

'Referringto Fig. 3, the relay R12 is the r u test relay, and is energized when the wiper ed finds an active eontact,' disconnects rotary relay R and in its lace eonnects vertical relay R19. The re R15 is used in testing for the individual Contact as -i battery supply relay for the calling subscriber. lllhen energized this relay disn the row relay B12. lThe denergiz- 'elay R12 disconnects the relay R15 in the test wiper w25 and connects it to clay l Relay R is the tip battery sup- Qly relay and controls the release magnets hlx and Irl* after the first selector switch S5 The relay E is so long as this Wiper encounters busy contacts, which are grounded through other switches.

Referring now to Fig. 4, relays R22 and R23 respond to impulses from the sending machine, Relay R23 receives the first set of imuulses belonging to the connector and causes the stepping magnet M11 of the switch S7 to step around so as to pick out generator current of the proper character. Operation of relay R23 closes the circuit of relay R2* Whose ,locking Contact rm isipon nected to the botto-1n contact of relay R22. lelay R23 also closes circuit of relay R27. rhis latter remains energized until the 'f called party answers or until the calling party hangs up his receiver. n case the called-for line is busy, relay R27 Will'be deenergized by action. of test relay R2". Relays E, R27 and R2 all have their circuits completed to Ground side of battery through wire 200, contacts om, w1, 147, T41? to ground. W hen the calling party hangs up his receiver after failing to get his party, switches S* and S5 are restored and ground reinoven from testA wire, causing denergi-` sation o any of the relays R24, R27 or R29 which happen to be locked. The Switch S7 is restored to normal after the ealledlsuh.- seriher hangs up his receiver orv when' the relays R2, l and R2* are denergized; and

fhe sleeve wiper Q04, in series with the cut-ofi' just `)er'ore it reaches its normal' position the.`

wiper :iran 'wel passes over a Contact and closes the circuit oi' Ythe release magnet M12 restoring the connector switch S(5 to normal position. Thus the connector switch S6 basa "uiclrrelease if theealled-o" line is busy,l and alter the called party answers a slow release by switch S7 which ,taires care of any accidental shaking of the receiver hook when the called-'party answers.

Referring to Fig. 5 relay B is the row test relay and R3 the individual test relay. `lelay it is the control relay and corresponds to relay R13 (Fig. 3). Relay R34 is the signal relay and pulls' up in series with relay R42 (Fig. after the primary trunk has found the line and the secondary switch S1 has found the trunk. The operation of this relay closes the circuits of the signal lamp L3 (Fig. (3), the guard lamp L2 and the night alarm bell. Relay 'R33 is the listening relay actuated by listening key LK. Operation of this relaydenergizes relays R32 and R43 and closes circuit of listening lamp L4. Relay R3 is the starting relay and is energized in series with R42 by the key SK. This relay disconnects relay R33 and connects the starting cam on the sending machine to stepping magnet Mf. 'It

also closes circuitot' guard lamp L2 and disconnects battery fronrthe first five contacts over which wiper' us30" sweeps. After arm'usw" passes the fifth contact it encounters battery potential and relay R33 is energized and connects interrupter I to inagnet Ml5 until arm uns mal position, cam springs 16T, 16S are lclosed, completing the cireiiitoi release magnet MZ, restoring switch S3 to its normal position. Relay R3T is the trunk start relay and is also used t'or release in case the calling subscriber has hung up his receiver or if the operator fails to get a response after pressing the listeningr key. This relay R37 is energized by key RK, which also actiiates relay R33. These two relays being energized at the same time remove battery connection from the vfirst, two contacts over which arm iesm" sweeps. In trunk calls, such as to wire chief, toll board, etc., 1t 1s only necessary to operate the first 'selector` Switch, which with the present sending machine requires only two rotations of the drum. The trunks of this class are wired directly to certain bank contacts of the first selector switches and not to the connector banks, for quick trunk service. After arm lwsm'passes the second contact the relay R35 is energized and operates as before. In case the calling party hangs up his receiver before the operator answers, relay R33 is energized in series with resistance coil 1' when the operator presses the listening key. which connects 'the tone test to the operators telephone set, whereupon she presses the trunk start button RK. The first selector switch Sl5 upon receiving the first rotary impulse. vfrom the sending machine through one of the buttons of 'the stripY K closes the foot springs 175 vand 176, he closure of these springs while relay R4 is denergized com pletes the circuit of release magnets M3 and M* causing the release of switches S4 and S3. Switch S* in restoring disconnects relay `R1 which opens circuits of relays R42, R3 yand R37. Relays R33 and R37 falling back 5 connect batteryto contacts 1.530 to 533", en-

raches its normal 4 ergizing relay R33 to restore switch S3 and S8. At any time during the building up of a connection the switches can be restored by the calling party in the manner described.

Referringr to Fig. G, number one key 'of each strip is connected to the pen ony the sending 'machine which transmits one impulse at each rotation; number two key to that which transmits two impulses, and so on to number ten key which .receives ten impulses. wire connected to one contact of each key in the strip and leading to its proper contact in the banks of the switch S3. The order in which these are arranged to transmit impulses in proper sequence-is as follows: At the first rotation of the sending machine the first strip of keys (hundreds) is connected to the tip side of trunk through switch arm ies and contact 133; second rotation, ten test impulses from disk D12 sent to sleeve side ot' trimk through arm w33 and rcontact 2333,' third rotation, selective ringing strip K* connected to tip side of trunk through arm 'w33 and contact 3.93,' fourth rotation, keys K2 (tens) connected 'to sleeve side through wiper w83 and contact 4.93"; fifth rotation, keys K3 (units) conn nected to tip side of trunk through arm e033; during the fifth rotation and just after the units impulses have been set, a single test impulse is sent to sleeve side of trunk through disk D13, wiper "ws30 and Contact 583; sixth rotation, arm 1033"" engages contacts connected to battery energizing relay R3". This relay unlocks R33, restores switches Each strip of keys has a common S3 and S3, thus disconnecting secondary switch S3 from the primary trunk in Fig. 3. The kick-olf switch S in Fig. Qlis provided for the purpose of preventing a defective trunk or operators circuit from re-l maining connected to thecalling line. -n a word, it is a time controlled element started when a call comes in and operating after a predetermined interval longer than the time required for full operation of the switches S4 and S3 in Figs. 3 and 5 respectively,

so that it' the connection from the line in one step in advance of the corresponding contacts over which wiper Iwal" sweeps. Relay R" 1s energized when switch S3 picks out a secondary switch S3 and partly closes circuit of magnet M. Wheirthe cam on the sendingr machine closes springs tl the eircuit 1s completed and switch S moves one insonne step at each rotation of the sending machine.

The maximum time for the secondary switch Ss to pick out the trunk terminating on the tenth contact in the tenth row would permit about two rotations of' the sending inaehine. As shown by the blank contacts in S the minimum time element for three rotations has been allowed and the maximum for six, dependinff upon the position of the Wipers of switch S" when relay R9 is energized. It" wiper ws1 has just passed inuitipled contacts 13110 it will then require three steps of Vswitch S before wiper wam finds battery potential to energize relay R7. .ln this case it would require three more steps for wiper ws to complete the circuit of relay R6. It Wiper wow is resting on multipled Contact 181 when relay R1 is energized, it will require only three steps of Wiper we before the circuit of the relay RG is closed. `When relay R6 operates it places ground on 218, 219,751, 3l, M to battery, operating magnet M to step Wiper wa to the next oontact and thereby unlock the relay R5 which 25 in turn denergizes relays R1?, R1 .and R3. The operation of relay RG also places ground on 21e, maar, 221, as (Fig. 5), 12e, in, through release magnet M18 to battery, causing the release of secondary switch Ss.

If for anyy reason the secondary switch after it is selected fails to make proper connection with thetrunk in Fig. 3 so as to ren lieve relays R33 and R5, the kiclooi' switch will come into play and between three and six rotations of the sending machine cause secondary switch S8 to be released and the switch S to piek out another trunk.

A second bank and Wiper are shown in switch S in dotted lines, Fig. 2, to indicate 4D `Jthe same method of connection, control and 4release for the primary switches (Fig. 3) by switch S. rfhe employment of this feature is optional, as in practice if switch S4 is left olf normal lamp L8 quickly attracts 45 .attention thereto and loealizes the trouble.

Operation: The subscriber at station A desiring aooiinection lifts' receiver R from hook H whichghridges his telephone across 7 line Wires lie-2, energizing releysR1 and R3 5.0 by Way of B, 19, 20, R3, 21, R, 22, '1121, l,

station A, 2, n2, 23,. ground to battery. Re-

lay R locks to..ground through F1724, andl r, and connects ground to individual test ,Contact c25 through 25 and r1, While R con 5 nects ground to row test contact 028 through 26 and rs1 end cornpletes circuit of group lampi., und relay R4, the former from B, 19, 27, L, 2S, fr, round to battery, the latter from B, 19, 29, 30, r3, to ground. Lamp L lights, and relay R4 completes circuit of stepping magnet `M to interruptor l for intermittent energization over the path, B,-19, M, 31, T51, 32 r, 33, lto ground. Magnet M moves switch S step by ste until wiper we engages a contact s connecte to relay 'R13 (Fig. 3) of an idle primary selector trunk, whereupon relays R and R13, (Figs. 2 and 3) are energized by current 19. 4l, R11, 42, R53 and ground. Relay Rui.

locks itself toibattery through #3243, rm,

44, and 34 to B; connects batteryto one terminal of relay R12, through 35, T133, 45, 4G, 11152, el?, and 48 and also completes circuit or rotary relay R113 through Vrm and interrupt-er l, so that this relay is energized intermittently, its circuit being: B, 3l, 35, am, 45, it, T152, 4.7, iai, 5o, Re, 5i, am, te, rm, l to ground. At each actuation of relay R11; magnet M5 is energized by current from B, 34, 57, contacts 58 of foot step switch F4, 59, M5, 53, 9'111, ground, stepping primary selector switch St around until Wiper lw2G engages row test Contact e211 whereupon vrelay R is energized over circuit B (Figl) ai, at, am, 4.5, 46, T152, i7, is, R12, is, we, c2, (Fig. 2) 2G, rs1, ground to buttery. Relay R12 locks itself to ground through rm, connectstest Wiper 'uf-5 to sleeve relay 'R15 through 54, 'ruf' and 55, and shifts inter# rupter from rotary relay R13 kto vertical relay R11 at T121, so that R19 is intermittently eneitgized over the circuit: B, 34, 35, we, 45, le, T152, i?, 491,. R19, 5c, 71123452, rm, I, ground, to battery. At 'each actuation of relay R1 Vertical :magnet it 1 is en ergiaed over the path B, 3st, 60, Vlld, 6l, P191 to ground, stepping switch S* up until wiper w25 engages individual test Contact c2is (Fig. 2) whereupon sleeve relay. R15 is energized. over the circuit: B, (Fig. 3), 3d, 35, 62, R1, 55, 71123, 54, w25, G25, (Fig. e), e5., r2 (of relay R), ground'to battery. Relay R15 connects battery to trunk conductor 7, by yWay of T151, 63, 6%, T141, 65, and resistance fr, and at the saine time opens the circuit of Relay R12 at Ms., Relay 12' opens circuit of rertical relay R19 and magnet M- is dee'nergized, which permits `wiper 7.0"5 to stop on contact ce, Wipers w3 and in* enga-ging contacts c3 and et, respectively. Tip relay B14 is now energized through subscribers telephone in series with R15. with the selection of the calling line as described, distributing switch S2, (Fig. 2) is stepped around in search of an idle sec- Simultaneously.

:ico

ical

ondary selector, bysrnagnet M2 in circuit :v B, f

is, inca, e?, te, im, ce, M2, to, am, 7i, i te ground. Switch S2 continues tostep around until Wiper arm we@ engages a Contact 820 connected to an idle secondary selector, whereupon relays R1 and R92, (Figs. 2 and 5) are energized in series, the circuit being: B, (Fig. 5), 86, springs 'i3-7l of operators pick J, 75, springs lli-47 ofoot step switch F8', 78, R32, 79, through Fig. 3 into Fig. 2,

ist 

